Air sensors have been utilized in the past to determine package build in the winding of various strand-type materials. Thus, in U.S. Pat. No. 3,845,912 an air sensor is shown which is utilized to sense the diameter of a forming package as it is being wound on a winder. As the package winds on the winder, air is introduced onto the surface of the package and flows backward into the sensor and a diaphragm associated with the air sensing device. The air returning to the device is amplified by the diaphragm and in response to the amplification of the pressure measurement, a pneumatic relay switch activates suitable mechanical equipment to move the package away from the air sensor as the package builds on the surface of the winder.
While the air sensing device shown in the aforementioned U.S. Patent serves a useful purpose in providing a necessary tool for sensing package build it is subject to certain restrictions. Thus it has been found that sensing devices of the type shown in the aforementioned patent are subject to imprecise functioning if the strand material being wound on the package is wet. Frequently water is trapped in the central passageway of such air sensing devices when the winder is stopped which causes improper signals when the winder is restarted thus causing the package being built on the mandrel to, in some instances, be improperly measured. In some instances improper measurement of the package diameter can result in damage to the package caused by the package striking the corner or front of the air sensing device itself.
Thus, in accordance with the instant invention a method and apparatus is provided which substantially eliminates the problems associated with water entrapment in the sensor. The method and apparatus provided by the instant invention substantially eliminates the problems associated with the prior art device in winding wet packages while utilizing air sensing devices similar to those shown in the prior art. Thus it is now possible in accordance with the instant invention to accurately measure package diameter as it is being built during a forming operation and to move the package as the diameter does build without damaging or in any way interfering with the winding of the strand material utilizing an air sensing device. The novel system permits the operation of air sensors to determine package build and to move packages away from traversing mechanisms as the package builds in accordance with such measurements while still providing adequate safeguards to insure against the improper reading of air pressures during the operation of an air sensor.